Structures as substances for catalysis for converting exhaust gas are typically formed of ceramic materials. In terms of reduction in pressure loss and thermal capacity to provide premature activation of catalyst, recently, reduction in thickness of cell walls has been requested. The thicknesses of the cell walls were in '80th, amount to around 0.15 mm (6 mil). The thickness of the cell walls, however, has been reduced nowadays to around 0.05 mm (2 mil).
On the other hand, the thickness reduction of the cell walls deteriorates the mechanical strength of the structures. This point has been compensated for by reducing the porosity of the structure to heighten the density. In the dense structure, the surface area of each cell is decreased, whereby it becomes difficult to deposit solids as catalyst carrier on the substances. This point has been compensated for by increasing the viscosity of the slurry, lowering the drawing speed of the slurry when flowing the slurry into the cells, lowering the blowing off speed of excess amount of the slurry from the cells, and so on.
Cross-reference: Japanese Laid-open public disclosure 2005-279436